Medical balloons are well known in the art. A conventional balloon assembly includes an expandable balloon fitted at the distal end of a carrier catheter, the catheter having at least one lumen fluidically connected to the internal volume of the balloon and arranged to supply fluid to expand, or inflate, the balloon, and to exhaust fluid from the balloon so as to collapse the balloon at the end of the medical procedure. Medical balloons of this nature are generally circular in transverse cross-section and have their two ends fixed in fluid tight manner to the balloon catheter such that the internal volume, or chamber, of the balloon is sealed to the environment. Whilst it is relatively simple to form a balloon which has a varying diameter along its length, it is harder to alter the cross-sectional shape of the balloon as the inflation pressure causes the balloon wall to tend to a circle. Attempts to make a balloon with cross-sectional shapes other than round when inflated have met with practical difficulties, including increased stiffness of the balloon particularly when deflated, increased tendency to rupture, poor repeatability and stability of the inflated shape, and so on.
Examples of medical balloons and catheters having a plurality of chambers of non-round cross-sections can be found in US 2007/0010845, U.S. Pat. No. 5,501,667, US 2015/0094657, U.S. Pat. No. 5,304,135, US 2003/0032963 and WO 2006/037608.